The general internet knowledge says. If there is two puncture wounds it means you got bitten by the fangs of a venomous snake.
I'd suggest being very careful with information about venomous snakes on the internet. The reason is the USA's traditional preponderance on that medium (particularly the English-speaking portion of it).
The USA is somewhat unusual in that almost all venomous snakes one is likely to encounter are Pit Vipers. These snakes have a special muscle for pumping venom through special extra-long fangs, so all they really have to do is poke you good with the fangs. That muscle also gives them a very recognizable triangular-shaped head.
The only real exception in the continental USA is the Coral Snake, which does happen to be super deadly, but is also very rare, shy, and geographically confined to the Gulf region. So in the USA traditionally a lot of helpful information created and published about dealing with "poisonous (venomous) snakes" is really just information about Pit Vipers.
In most of the rest of the world, the dangerous venomous snakes you are likely to run into are much more likely to be elapids (like the Coral Snake). As one of the comments mentioned, these snakes have very small fangs, and generally have to chew a bit on the victim to get a good injection. So with a bite from one of them, most likely you'll see more than just two small punctures.*
However, if you happen to be US-based as well, this is probably pretty good advice. Just don't go around thinking its applicable worldwide.
* - I think the victim is also unlikely to live from a good elapid bite, so perhaps practically the advice still holds in this case.
According to this article: How to identify and treat snake bites - yes this does seem to be something which some people state as accurate.
Venomous snakes have two fangs that deliver venom when they bite. A venomous snake bite will usually leave two clear puncture marks. In contrast, a nonvenomous bite tends to leave two rows of teeth marks.
However, there are more symptoms to bear in mind as well:
It can be difficult to tell the difference between puncture wounds from venomous and nonvenomous snakes. People should seek medical attention for all snake bites. The typical symptoms of a venomous snake bite include:
- two puncture wounds
- swelling and pain around the bite area
- redness and bruising around the bite area
- numbness of the face, especially in the mouth
- elevated heart rate
- difficulty breathing
- blurred vision
- excessive sweating
Therefore whilst this may well be a fact, it may not be reliable when diagnosing a bite. You're going to be better off getting some idea of what the snake is. This would be dependant on the area you're in, so make sure to get a good idea of the species in an area you plan to travel where it is likely you may risk a bite.
From my React Right first aid course material (sorry can't actually link to this) one of the restirctions on treating a snake bite state:
If possible, identify but do not attempt to capture or kill the snake.
As medical providers will need to know what the snake is, and it could be hard to tell from your swollen, red, painful bite wound.